Magnetism and Moving Charges Practice Test

A rectangular current loop (dimensions $0.10,\text{m}\times0.20,\text{m}$) carries current $I=2.0,\text{A}$, meaning charges move around the loop and create a magnetic dipole moment $\vec\mu=IA,\hat n$. The loop is in a uniform magnetic field $\vec B=0.30,\text{T}$ to the right. The torque on the loop is $\vec\tau=\vec\mu\times\vec B$; equilibrium occurs when $\vec\mu$ is parallel or antiparallel to $\vec B$. Refer to the scenario above. Determine the net force on the loop in the uniform magnetic field.

In a uniform magnetic field region, $\vec B=0.25,\text{T}$ directed out of the page. A positive charge moves upward at $v=2.0\times10^5,\text{m/s}$. Moving charges create magnetic fields, and in an external field the charge experiences the Lorentz force $\vec F=q,\vec v\times\vec B$, which is perpendicular to both vectors. Refer to the scenario above. What is the direction of the magnetic force on the positive charge?